Magnetron modot



May 21,v 1940. E Q UNDE f' Re. 21,458

MGNETRON MODULATOR Y I y Original Filed Jan. 51, 1956 3 Sheets-Sheet 1Figi@ ffb. Fzgfe May 21, 1940. E. G. UNDER MAGNETRON MODULATOR OriginalFiled Jan. 3l, 1936 3 Sheets-Sheet 2 56 I 7 #mu fx@ May 21., 1940 E. G.UNDER MAGNETRN MODULTOR Original Filed Jan. 31, 1936 5 Shasta-Sheet 5fnv/ernia?- Ressued May 21, 1940 UNITED STATES Re.'21,45s

PATENT OFFICE MAGNETRON MODULATOR Ernest G. Linder, Philadelphia, Pa.,assigner to Radio Corporation of America, a corporation of Delaware 9Claims.

lator. More particularly, my invention relates to the modulation ofmagnetrons by moving the anode with respect to the cathode, or by moving5 both electrodes with respect to the permanent magnetic field of themagnetron.

A magnetron is a thermionic tube including one or more anodes, acathode, and a magnetic field. The lines of force of the field aresubstantially 10 parallel to the cathode. The electrons from the cathodefollow a curved path 2 which may be illustrated by Figure IA. The curvedor circular path is due to the forces exerted on the electrons by themagnetic field, the anodes 5, 1, and the l5 cathode 3.

In contrast to the magnetron, an ordinary triode has a cathode, grid andanode. No magnetic field is required. The electrons travel in asubstantially straight line from` the cathode to the B anode. The numberof electrons which reach the anode is normally determined by the spacingof the electrodes, and the relative grid, anode and cathode potentials.

I am aware of ordinary electron tubes in which 25 the electrodes havebeen relatively movable. 'I'he movement of electrodes in such tubes hasslightly varied the number of electrons reaching the anode, or theamplification factor if a triode is used. In the case of a diode ortriode relatively small 30 movement of the electrodes will have asecondary eect on tube operation.

The operation of a magnetron is especially suited to modulation byrelative movement of electrodes or of electrodes with respect to the gmagnetic eld. Since the magnetron is used at ultra-high frequencies, thecapacity between the anodes is of primary importance. tive movement willhave a very large eiect on the operating frequency. Furthermore, thecircular lo path of the electrons makes it possible to completely stopthe flow of electrons to one anode and to greatly increase the electron110W to th other.

Since the electron path is dependent upon the L5 lines of force of thepermanent magnetic field, the operation of the magnetron will be greatlyaffected by a slight relative movement of the electrodes with respect tothe field. By Way of example, the effect of moving the anodes with re-;0 spect to the cathode is illustrated in Fig. IB and Fig. IC. Othertypes of relative `movement will vproduce large changes in anodecurrent. These lchanges are due to the characteristic magnetronoperation.

g One of the objects of my invention is to modu- A slight relan (Cl.Z50-27.5)

My invention relates to a magnetron modulate a magnetron by changing therelative spacing .of the cathode and anode electrodes.

v Another object is to modulate a magnetron by moving the cathode andanode electrodes with respect to the magnetic field. 5

- Another object is to change the relative spacing of the magnetronelectrodes by means of a sound operated diaphragm. l

Another object is to vary the operating frequency of a magnetron bymoving its electrodes in a non-uniform eld.

A further object is to operate a single magnetron as an oscillator,modulator and microphone.

A still further object is to vary the frequency l5 of a magnetronoscillator by varying the interelectrode capacitance.

An additional object is to provide means Whereby a magnetron may be madeto generate audio frequency currents.

Reference is made to the accompanying drawings in which Figure IA,Figure IB, and Figure IC are illustrative of the operation of amagnetron embodying my invention,

Figure 1I is a schematic diagram of a mag- :25

netron oscillator including modulation means,

Figure III is an illustration of a magnetron modulated by a soundactuated diaphragm,

Figure IV is a schematic diagram of a modification of Figure I,

Figure V is a schematic diagram of a magnetron in which the anodes aremoved with respect to cathode for frequency modulation,

Figure VI is a schematic. diagram of a magnetron in which the tube andelectrodes are .35 moved with respect to a magnetic field of nonuniformcharacteristics.

Figure VIa represents the anodes and the electro-magnet for producingthe non-uniform eld of Figure VI, l40

Figure VIb is a plan view of the tube moving l means shown in elevationin Figure VI.

Figure VIc is a plan view of the pivotal mounting and biasing springshown in elevation in Figure VI.

Figure VII is a schematic diagram of a magnetron similar to Figure VI inwhich the tube moving means is a sound actuated diaphragm, and

Figure VIII is a modification of the apparatus of Figure VII.

Throughout this specication similar reference numerals will be used todesignate similar parts.

In Figure II within an evacuated glass envelope l are mounted a cathode3 and a pair of anodes ,55

5, 1. The cathode is energized by a battery 9. The anodes are connectedto a pair of lead wires II, I3. A conductor I5 connects the lead wires.This conductor I5 and the anodes 5, 1 form a resonant circuit.

The lead wires I, I3 may form a transmission line which may Vbeconnected to a dipole antenna or the like. The negative terminal of ananode battery I1 is connected to the cathode 3. 'I'he positive terminalof the anode battery is connected to a bridging conductor I9 which issuitably located on the leads II, I3.

A U-shape magnetic core `2| is energized by a core 23 and a battery 25.Suitable jaws (not shown) are attached to the pole pieces of the core 2|to clamp'the envelope I. The magnetic lines of force between the polepieces surround and are substantially parallel to the cathode 3. 'Ihearrangement thus far described may be operated as a, magnetronoscillator.

A series of corrugations 21 are formed in the section of the `envelopeadjacent the lead-in of the transmission wires II, I3. A connecting link29 is xed to the end of the envelope adjacent the corrugations 21. Amagnetic armature 3| is fastened to the end of the link 29. Anelectromagnet 33 is suitably positioned with respect to the armature 3|.The winding of the electromagnet is serially connected to a localbattery 35 and a microphone 31.

The corrugations 21 offer suicient flexibility to the envelope I topermit movement of the corrugated end of the envelope with respect tothe portion clamped by the jaws -attached to the magnetic core 2|. Aslight movement of the corrugated end which also supports the lead wiresII, I3 causes a substantial movement of the anodes 5, 1 with respect tothe cathode 3. This movement results in a change of electrondistribution represented by Figs. IB to IC". 'I'his change will modulatethe normal electron flow.

While I have illustrated the electromagnet 33 and microphone 31 as aconvenient means of flexing the tube to effect modulation, it should beunderstood that other means may be employed. For example, a soundactuated diaphragm, a mechanical movement for telegraphic signalling,`or amplifiers may be used.

In Fig. III, the circuit is representative of a magnetronmicrophone-amplifier. In this device the magnetron operates as amicrophone and also as an amplifier, although amplification is notessential. The leads II, I3 are connected to the primary 39 of thepush-pull transformer 4I. The anode battery I1 is connected to thecenter tap of the primary 39. 'Ihe secondary 43 of the transformerrepresents the output of the device.

In place of the electromagnetic motor of Figure II, a sound operateddiaphragm 45 has been connected to the link 29. A movement of thediaphragm is transmitted through the link 29 to the exible end of theenvelope I. 'Ihe movement of the envelope in turn varies the relativeposition of anodes and cathode. This alters the electron distributionand hence the current flow through the primary 39.

A modification of Figure II is illustrated in VFigure IV. Thismodification consists primarily in substituting a flexible metal section41 in place of the corrugated glass section of envelope I. As is knownto those skilled in the art, a suit- ,able metal may be attached toglass by sealing.

The seal oers an airtight bond between the glass envelope I and themetal envelope 41. 'I'he free end of the metal envelope includes a glassinsert 49 through which cathode leads may be brought.

In this modification, the cathode 3 is moved with respect to the anodeelectrodes 5, 1. The electro-magnetic motor device represented byarmature 3| and magnet 33 has been connected through links 5|, 53 andlever 55. The lever is pivoted at 51. The single link 29 of Figure Ilmaybe used in place of the links and lever.

Likewise, the diaphragm 45 of Figure III may be Various movements of theanodes may be obtained by proper phasing of the exciting currents. Thespaces between the armatures 6|, 63 and the walls of the envelope aresuflicient to permit free movement of the armatures. The bridgingconductor 69, which may be employed in a magnetron oscillator, hassunicient length and flexibility to permit movement of the lead wiresII, I3. v

Since the anodes 5, 1 are attached to the lead wires, they may be movedwith respect to each other, or With respect to the cathode 3. If themagnetron is oscillating as a negative resistance device, theoscillatory frequency is inversely proportional to the capacity betweenthe anodes; therefore, the movements of the anodes with respect to eachother will substantially vary their capacities and the oscillatoryfrequency. If the m-agnetron is oscillating as an electronic oscillator,variations in relative anode spacing will vary the amplitude ofoscillations. Thus, the magnetron oscillator of Figure V may befrequency modulated by impressing currents of the desired modulationfrequency on the electromagnets 65, 61.

The arrangement of Figure V may be employed as microphone-amplifierinstead of an oscillator. As an amplifier, the bridging conductor may beomitted. In both cases, the magnetic eld is used. The electro-magnetstructure 2|, 23, 25 of Figure II is suitable for this purpose. A Ushape permanent magnet may be used as shown in Fig. V.

Instead of using the arrangement of Figure V as a microphone-ampliercombination, this device may be used to generate audio frequencycurrents. In the generation of audio frequency currents the microphone31 is omitted. A portion of the output currents, in the proper phase, isfed back to the exciting magnets 65, 61. The feedback currents may beamplified by a triode or the like. audio currents can be controlled byadjusting the natural frequency of vibration of the anodes 5, 1,armatures 6I, 63 and lead Wires I I, I3.

Figure VI represents a magnetron oscillator The frequency .of ther oramplier which is moved as a Who-le by the ytory currents, or theampliiication, depends upon V7 vthe magnetic eld strength, modulationwill be effected by the relatively varying eld. 'This arlrangement isbest adapted to the electronic mode of oscillation.

In Figure VI, the envelope I is suitably fastened to a pivot member 1|.The pivot member 1| is pivotally supported by a yoke member 13. One ormore biasing springs 15 are connected between fixed studs 11 on the yoke13 and the pivot member to yieldably position the tube. These biasingsprings may be helical in form similar' to the hair spring on a watch.

The electro-magnetic system of this figure differs from the precedingfigures. In the preceding gures, the pole pieces of the core 2| were ofnormal uniform shape and produced a substantially uniform field. Thepole pieces 15 for this embodiment of my invention are illustrated inFigure VIa. The effect of the slanting pole pieces 19 is to produce amore dense magnetic Ifield between the near points and less densebetween the more widely spaced points. Movement of the anodes 5, 1 andcathode 3 in the non-uniform eld will be equivalent to varying the eld.This variation modulates the anode current or varies the frequency ofoscillation.

In place of slanting pole pieces, various shape pole pieces may be used.For example, aV or inverted V-shape pole piece or a conical shape Willhave the required non-uniform eld. Where the eld has a rate o-fvariation which is uniform with respect to movements on either side ofthe cathode, push-pull modulation may be produced.

The non-uniform iield may be used for purposes other than modulation.For example, a permanent magnet may be substituted for the electricalone and the operating frequency of the magnetron varied by moving themagnet with respect to cathode and anode. Such a system lends itself toportability and simplicity of frequency adjustments.

One means for moving the magnetron of Figure VI is illustrated as anelectro-magnetic driver 8|. 'Ihe driver is shown in plan view in FigureVI and in elevational view in Figure VII). A pair of arms 83 are rigidlysecured to the envelope I. A magnetic armature 85 is secured to the endsof these arms by soldering, welding or the like.

'I'he biasing springs 15 normally position the armature 85 in the centerof the air gap of a magnetic core 81. 'Ihe air gap is of sufcient Widthto permit the armature to freely oscillate within the gap when themagnet is energized. The energizing means includes the eld coil 09,battery 9| and microphone 93. Ampliers and lever actions may be employedin place of the direct drive shown.

A modication of Figure VI is illustrated in Figure VII. The essentialdifference between the apparatus of Figure VI and Figure VII is that thelatter has a sound actuated diaphragm 95 to actuate the magnetron withrespect to the non-uniform field. This eld is produced by a magnet whichhas slanting pole pieces 19 similar to those shown in Figure VIa.

The diaphragm 95 may be a cone of suitable size. A exible strip 91 ofleather or cloth connects the cone to a rigid supporting ring 99. Thecenter of the cone is connected to the movable end of the magnetron by alink IOI. Sound impressed on the diaphragm actuates the magnetron whichis pivotally mounted as previously described. 'I'his combination maybeused as a microphone, microphone-amplifier, or oscillator, modulator andmicrophone.

In the embodiment of my invention shown in Figure VIII, the magnetron ismounted so that it may be rocked about the axis of envelope I. A pair ofmetal rings |03 are clamped at the ends of the envelope I. A pair ofwires |05 are attached to each of the rings. These pairs of wiresterminate in supports |01.

The pairs of wires and their connections act as a torsional balance. Thesuspended magnetron may be rocked about the axis of its envelope In thisfigure, the batteries and connecting leads have been omitted. 'I'hemagnetron may be connected and adjusted for genillustration, asoundactuated diaphragm 95 is shown. The diaphragm 95 is coupled to theenvelope I by suitable links IOI, |09. The force applied through theselinks rotates the magnetron about the axis of envelope I. The eld in thepresent instance is of the uniform type. l

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Normally, the magnetic ,lines of force are sub- 1 stantially parallel tothey cathode 3. As the magnetron is rocked back and forth, the relativeangular relation between the electrodes, and the magnetic lines lisvaried. This variation alters the electron now and thereby modulates theoutput.

Thus I have described, and illustrated several embodiments of myinvention by means of which a magnetron may bel used as a microphone,microphone-amplifier, modulated oscillator, a modulator, or audiofrequency generator. Various elements of each of the severalarrangements may be added to or substituted for elements of the othercombinations. For example, a diaphragm may be substituted for theelectromagnetic driving motors and vice versa.

I claim as my invention:

l. A magnetron including a cathode electrode and spaced from saidelectrode a pair of anode electrodes, means for creating a magneticfield whose lines of force surround and are substantially parallel tosaid cathode and an electromagnetic motor for varying the orientation ofsaid electrodes by relative motion of said electrodes.

2. A magnetron including van evacuated envelope having a rigid sectionand a flexible section, an electron emissive cathode electrode supportedby one of said sections, and a pair of anode electrodes supported by theother of said sections, means for establishing a magnetic neld tothereby cause electrons emitted from said cathode to travel curved pathsto said anodes, and means for exing said flexible section so that saidcathode and anodes may be moved relative to each other to thereby varythe number of electrons traveling between said cathode and anodes.

3. A magnetron including an evacuated envelope having a rigid sectionand a flexible metallic section, an electron emissive cathode electrodesupported by one of said sections, means for establishing a magneticlfield to thereby cause electrons emitted from said cathode to travelcurved paths to said anodes, and a pair of anode electrodes supported bythe other of said sections, and means for flexing said metallic sectionso that said cathode and anodes may be moved relative to each other tothereby vary the number of electrons traveling between said cathode andanodes.

electrode and spaced from said cathode electrode a pair of anodeelectrodes, means for creating a magneticeld whose lines of forcesurround and aresubstantially parallel to said cathode,

lsaid eld having such a value that the electrons which are released fromsaid cathode move substantially tangentially to said anode electrodes,

' means for moving said anode electrodes With respect to said cathodeelectrode in accordance with a signal so that the electron current toone of said anode electrodes is increased by a movement which decreasesthe electron current lto the other of said anode electrodes, whereby acurrent is produced Whose variations correspond to said signal. I

6. A device for producing modulated ultra high frequency oscillationscomprising a magnetron oscillator including a cathodeelectrode andspaced therefrom a pair of anode electrodes, means for producing amagnetic eld Whose lines of force surround and are substantiallyparallel to said cathode electrode, and means for producing relativemovements between said electrodes to vary the characteristics of saidoscillations in accordance with said movements.

7. A magnetron including an evacuated envelope having a rigid sectionand a flexible section, an electron emissive cathode electrode supportedsolely by one of said sections, and a pair of anode electrodes supportedsolely by the other of said sections, means for establishing a magneticfield perpendicular to the path of electron flow to thereby causeelectrons emitted from said cathode to travel curved paths to saidanodes, and means for flexing said flexible section so that said cathodeand anodes may be moved relative to each other to thereby vary thenumber of electrons traveling between said cathode and anodes.

8. A magnetron microphone-oscillator modulator comprising an evacuatedenvelope having a rigid section and a flexible section, an electronemissive cathode supported solely by one of said sections and a pair ofanode electrodes supported solely by the other of saidy sections, meansfor establishing a magnetic field parallel to the axis of said cathodeto thereby establish ultra high frequency oscillations, and means forflexing said fiexible section in accordance with sound pressurevariations so that said oscillations are modulated in accordance withsaid variations.

9. A magnetron including a cathode electrode and spaced from saidelectrode a pair of anode electrodesmeans for creating a magnetic fieldWhose lines of force surround and are substantially parallel to saidcathode and means for varying the orientation of said electrodes byrelative motion of said electrodes,

ERNEST G. LINDER.

